Cutting insert with trapezoidal indentations along the cutting edge

ABSTRACT

The invention relates to a cutting insert for chip-forming machining, in particular for roughing of metallic work-pieces with a high feed speed. To increase the chip movement during cutting it is suggested that indentations (14) be provided in the region of a cutting edge (12) which are arranged in a row extending along the cutting edge (12), which interrupt same and which have a generally trapezoidal sectional shape parallel to the cutting edge (12) and perpendicular to the chip surface (10) with trapezoidal sides open toward the chip surface, the indentations having a chip-surface base extending at a negative or 0° chip angle (19) to the cutting edge (12), the chip surface (16) in the region between the indentations (14) at the cutting edge (12) has a positive chip angle (17).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US national phase of PCT applicationPCT/DE92/01027 filed 7 Dec. 1992 with a claim to the priority of Germanapplication P 41 41 368.7 filed 14 Dec. 1991.

FIELD OF THE INVENTION

The invention relates to a cutting insert for chip-forming machining, inparticular for rough machining of metallic workpieces with a high feedrate having a chip surface which is provided in the region of a cuttingedge with indentations which are arranged in a row extending along thecutting edge, which interrupt same and which have a generallytrapezoidal sectional shape parallel to the cutting edge andperpendicular to the chip surface with trapezoid sides open toward thechip surface.

BACKGROUND OF THE INVENTION

Cutting inserts of this type are known from the prior art, e.g. from EP414,241. Such a cutting insert has indentations on its edge surface aswell as on its chip surface which overlap in the region of the cuttingedge so that the cutting edge is set back in the region of theindentations relative to the remaining portions of the cutting edge. Theactual trapezoidal shape has sharp edges which are hard to maintain forlong times. In addition even with this arrangement the friction as chipspass over it is considerable. Disadvantageously the cutting insert inthis reference can only be used for a particular setup.

Further cutting inserts with indentations are known from German2,849,610. As a result of the substantial width of the inserts at theactual cutting edge a substantially increased plastic deformation orstiffening of the passing chips is achieved. The indentations are in topview generally round to square with rounded transitions and cornerregions in the chip surface. A comparable cutting plate is described inU.S. Pat. No. 4,447,175 where a row of concave recesses is providedalong the cutting edge with the cutting edge uninterrupted. The recessesare generally rectangular seen in top view.

U.S. Pat. No. 3,973,308 also describes recesses that are in top viewrectangular or even triangular and that also do not reach to the cuttingedge but start in a region at a bevel of the cutting edge and thatextend inward down into a chip groove. This embodiment also is intendedto reduce the temperature and forces exerted on the chip surface duringmachining.

Similarly to reduce the thermal and mechanical load during machiningoperations German 3,731,426 suggests a cutting insert with a corrugatedcutting edge where the chip surface is corrugated parallel andperpendicular to the cutting edge.

OBJECTS OF THE INVENTION

It is an object of the present invention to develop a cutting insert ofthe above-described type which has even at high feed speeds a stableguiding and diversion of the chips with minimal wear to the cuttingedge. Furthermore the cutting insert should be simple in constructionand also simple to make.

ACCORDING TO THE INVENTION

The solution is the cutting insert which is characterized in that theindentations have a chip-surface base extending at a negative chip angleor a 0° chip angle for the case of an indentation with a positive chipangle. The chip surface in the region between the indentations at thecutting edge has a positive chip angle of at least 5°. To avoidsharp-edge transitions between the indentations and the surrounding chipsurface in the region of the cutting edge the transitions are preferablyrounded, preferably with a radius from 0.3 to 3 mm.

This cutting insert causes a plastic deformation of the chip passingover it with minimal force and friction. The chip shaping as well as thechip guiding are positively influenced by the negative chip angle of theindentations. In general the negative chip angle of the indentationsinterrupting the cutting edge stabilizes the cutting edge so that highfeed rates can be used without the danger of breaking off parts of thecutting edge. The trapezoidal section is not only clearly defined duringmanufacture of the cutting insert but can be made without great costwhich works out cost efficiently. In addition according to theapplication the cutting insert is to be put to, variations are possiblesuch as conforming the depth of the indentations to the use conditions,that is the cutting speed, cutting depth, feed rate, and the type ofworkpiece being machined. The chips are deformed and deflected, incontrast to most of the prior-art systems with bumps or grooves in thechip surface, directly at the cutting edge and the type of deformationis set in accordance with the depth and width of the indentationsrelative to the surrounding chip surface.

The positive chip angle substantially increases the cutting capacity andthe feed rate.

preferably the trapezoidal shape of the indentations is axiallysymmetrical to a perpendicular from the cutting edge, that is both sidesof the trapezoid are at the same angle to the chip surface or thechip-surface base of the indentations. In this manner one-sided orpoint-like overloading of the cutting edge is avoided.

According to a further embodiment of the invention the indentations atthe cutting corners each have trapezoidal sides with a steep inclinationangle and/or narrow trapezoidal bases and/or small spacings between theindentations. In particular in the cutting-corner region one can deviatefrom a uniform shaping of the indentations so that the corner that isheavily loaded by the chip section greatly deforms the passing chip inorder to give the necessary stiffness to ensure the desired chipbreaking.

preferably the trapezoid side angles measured at the negative chipsurface are between 110° and 160°. The negative chip angle of thetrapezoid base of the indentation lies between 0° and 20°, preferablybetween 5° and 15°. The positive chip angle of the chip surfacesurrounding the indentations is between 5° and 25°, preferably 5° and20°. It has further been shown to be advantageous to set the spacings ofthe indentations smaller than the width of the indentations.

The formation of the indentions seen in a top view on the chip surfaceis optional but a narrowing of the indentations toward the chip-surfacecenter in a trapezoidal or triangular shape causes the neighboringregions of positive chip angle to also converge toward the cutting edgeand thus enter like a wedge into the material being machined.

There are also advantages in manufacturing. Preferably the geometry ofthe indentions seen in a top view on the chip surface are trapezoidal.The width of the indentations at the cutting edge is between 0.5 and 4mm so that at least three or four indentations can be formed on eachcutting edge. The relationship of width to depth of the indentations is6:1, preferably according to profile 3:1 or 4:1.

According to a further embodiment of the invention the cutting edge hasa bevel whose angle with the positive chip-surface region between theindentions is the same as the angle between this bevel and the negativechip-surface base of the indention. In other words the bevel follows thegeometrical path of the surfaces which are behind the bevel. Thisreduces stress on the chip in the edge region at the bevel so as toreduce compressing and breaking it. This angle lies according to afurther embodiment of the invention between 160° and 170°. To furtherdestress the chip the indentation and/or the surrounding chip surface isformed with an additional chip groove.

Additional chip forming can be done by raised chip-forming elements,preferably shaped as pyramidal or conical frustums, when the chipsurface surrounding the indentation is formed at a spacing form thecutting edge with such chip-forming elements.

In addition the chip surface has along the cutting edge from cuttingcorner to cutting corner a convex or concave envelope curve so that thedepth and/or spacing of the indentations increases from the cuttingcorners to the cutting-edge middle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a cutting insert;

FIG. 2 is a cross section taken along the line 1--1 of FIG. 1;

FIG. 3 is a section taken along the line 2--2 of FIG. 1;

FIG. 4 is a section taken along the line 3--3 of FIG. 1;

FIG. 5 is a section taken along the line 4--4 of FIG. 1;

FIG. 6 is a section taken along the line 5--5 of FIG. 1;

FIG. 7 is a section taken along the line 6--6 of FIG. 1;

FIG. 8 is a section taken along the line 7--7 of FIG. 1;

FIG. 9 1s a section taken along the line 8--8 of FIG. 1;

FIG. 10 is a section taken along the line 9--9 of FIG. 1;

FIG. 11 is an enlarged detail view of a cutting edge;

FIG. 12 is a perspective view of the cutting edge according to FIG. 1;

FIG. 13 is a top view of a cutting insert with a perspective free angle;

FIG. 14 is a section taken along the line 10--10 of FIG. 2;

FIG. 15 is a section taken along the line 11 of FIG. 2;

FIG. 16 is an elevational view in a plane of the line 12--12 of FIG. 2in a cutting position;

FIG. 17 is a view similar to FIG. 3 but illustrating a differentembodiment;

FIG. 18 is another view similar to FIG. 3 showing still anotherembodiment;

FIGS. 19 through 26 are respective partial sections of variousembodiments of cutting edges;

FIG. 27 is a top view of a cutting insert according to the invention inanother embodiment;

FIG. 28 is a section along the line 13--13 of FIG. 5;

FIG. 29 is a section along the line 13--13 of a modification of theembodiment of FIG. 5;

FIG. 30 is a section along the line 14--14 of FIG. 5 of the embodimentcorresponding to FIG. 5;

FIG. 31 is a section along the line 14--14 of FIG. 5 of the embodimentof FIG. 5;

FIG. 32 is a fragmentary view of an embodiment or a cutting edge with aconvex shape;

FIG. 33 is a fragmentary view of a cutting edge with a concave shape;

FIGS. 34 and 35 are top views of cutting inserts in the workingposition;

FIGS. 36 to 44 are respective front views of the edge surface of variousembodiments; and

FIGS. 45 to 47 are top views of further embodiments of the invention.

SPECIFIC DESCRIPTION

As shown in FIG. 1 the cutting insert has a chip surface 10 which formsa cutting edge 12 together with each of the edge surfaces 11 whichextend perpendicular or at a free angle thereto. In this case the plateis rhombic and thus has four cutting corners 13. This principle appliesfor the formation of the cutting insert in other shapes, e.g.triangular. Each cutting edge is formed with and interrupted byindentations 14 which extend in a row running along the cutting edge 12.These indentations have seen in cross section or in a side view at theedge surface a trapezoidal shape where the shorter of the two parallelsides of the trapezoid form the indentation and the sides of thetrapezoid diverge toward the chip surface 10.

The cutting insert shown in FIG. 1 also has a peripheral bevel or 1 and15 around the cutting edge 12.

As seen in FIG. 2, FIG. 4, FIG. 6 and FIG 8; the bevel 15 runs at anangle of about 90° to the edge surface 11. A descending chip-surfacepart 16 forms an angle 17 of 5° to 20° with the bevel 15. As visiblefrom the sections of FIG. 3, FIG. 5, FIG. 7 and FIG. 9 an indentation 14is formed between the abovedescribed chip surface portions along whichthe bevel 15 also runs.

The indentation has a chip-surface base 18 which is inclined at an angle19 of about 10° to 15° to the horizontal so that it runs negatively. Asalso particularly visible in FIG. 12 the angle of the bevel 15 to thedescending chip-surface part 16 on the one side and to the chip-surfacebase 18 on the other side are the same. Here the bevel is morenegatively inclined toward the cutting edge in the region of the cuttingedge than the chip-surfaces base 18 of the indentation.

As visible in FIGS. 1, 11 and 12 the indentations 14 are aligned in arow along the cutting edge 12 at spacings that can be the same ordifferent. As visible from the section of FIG. 10 of the indentations 14alternate with the chip-surface regions 16 likes hills and valleys. Thetransitions from the indentations 14 to the chip-surface parts 16 areformed rounded. Normally the trapezoidal shapes of the indentations 14are made symmetrical, that is the trapezoid side angles 20 and 21 arethe same size, here 45°. With this inclination angle 19 of the cuttingsurface bases 18 of the indentations 14 there is a depth 22 relative tothe bevel 15 or chip surfaces 16. The transition from the trapezoidsides 25 to the chip-surface base 18 has rounding like the transitionfrom the trapezoid side 25 to the bevel 15 or to the chip surface 16.With uniformly spaced indentations the width 24 of the positivelyinclined chip surface 16 as well as the width 23 of the chip-surfacebase 18 running at a negative chip angle 19 are defined. As alsodescribed below the height 22 and the trapezoid-side angle 20 can bevaried with respect to the width 23 or 25 in order to conform thecutting insert to other desired cut conditions. As clearly shown in FIG.1 the trapezoid side 25 closest to the cutter corner can be formed witha larger trapezoid angle 20 (see FIG. 11), that is the trapezoid sidecan run more flatly to the cutter corner.

The cutting plate shown in FIGS. 13 to 15 is generally square and hascutting corners 13 provided with bevels. Four recesses 12 extend alongthe cutting edge 12 and have cross sections with positive chip angles 17or negative chip angles 19. In contrast to the embodiments shown inFIGS. 2-10 here the cutting edge is formed by the chip surface 16 andthe negatively set edge surface 11 or the cutting surface base 18 andthe surface 11. The cutting edge 12 is set somewhat back in the regionof the indentations 14.

In FIGS. 16 through 18 several variations on the depths 22 and thetrapezoid side angles 20 and 21 are shown. As visible in FIG. 16 thewidths of the chip surface regions (here 241 to 243) surrounding theindentations 14 are larger as the distance from the cutting edge 13increases. The width 23 of the cutting surface base 18 remains constant.Thus the spacing of the indentations 14 from each other is greater withlarger distance from the cutting edge 13.

Simultaneously the spacing varies from the chip surface regions 16 to aplane 28 connecting the cutting corners 13. In this case there is aconcave cutting edge path from a cutting corner 13 to the next cuttingcorner since the spacing 271 (equal to 0) to 273 increases. Meanwhilethe base plane 29 defined by the chip-surface bases 18 of theindentations 14 is constant.

In the embodiment according to FIG. 17 the common envelope curve of thechip surface regions 16 lies in the region of the above-defined plane28. Above all the depth of the indentations increases with increasingdistance from the cutting corner 13 which is seen in ever smallerspacings 291 to 294 relative to a randomly selected plane 29. In thesame manner the spacings 241 to 243 grow as in FIG. 16.

Another possible embodiment is the change of the trapezoid angles 201and 211 to 202 and 212 which become greater with greater spacing fromthe cutting corner like the necessarily increasing spacings 301 to 303of the indentations measured middle-to-middle in the same way. It isunderstood that the embodiments of FIGS. 16 through 18 can be puttogether in combinations of the invention.

Further embodiment variants are shown in FIGS. 19 to 26 which aresections perpendicular to the cutting edge 11 in the region of anindentation 14. In the embodiment shown in

FIG. 19 the chip surface 16 and the chip-surface base 18 run convexlytoward the cutting edge. The chip angle at which the chip surface 16meets the cutting edge is at least 0° or positive while the chip surfaceangle of the chip-surface base 18 is negative.

According to FIG. 20 the cutting insert has right next to a horizontallyrunning bevel 15 a raised chip-forming element 31 which is partspherical, frustum shaped, or elongated. The chip-surface base 18 runsconvexly but under a negative chip angle. In addition the entire widthof the indentations or the center of the indentation has a raisedfurther chip-forming element creating a corrugated shape correspondingto FIG. 20.

The chip surface regions 16 and the base 18 according to FIG. 21 aresimilarly concave but both surfaces end at a positive chip angle in theregion of the cutting edge.

The embodiment according to FIG. 22 corresponds to the FIG. 19embodiment except that right next to the convex path of the chip surface16 and thus behind the indentations there are chip-forming elements 32along the cutting edge which correspond to the above-describedchip-forming elements 31.

FIG. 23 shows the embodiment variant of a convex chip surface 16 and aconcave chip-surface base 18.

According to FIG. 24 the chip surface 16 and the chip-surface base 18are also convex and both regions 16 and 18 have a groove 33 and 34 whichruns toward the chip-surface center.

FIG. 25 shows a cutting insert with a concavely descending chip surface16 and a convex chip-surface base 18. In the embodiment shown in FIG. 26the cutting edge has a bevel 15 which follows the contours of the chipsurface 16 and that of the indentations. The bevel has in this case anegative chip angle. Variations on the individual features of theembodiments shown in FIGS. 19 through 26 are possible. FIG. 27 shows asquare cutting plate which has a central chip surface 10 which can beeither recessed with respect to the highest part of the cutting edge(FIGS. 28 and FIG. 30) or raised (FIGS. 29 and FIG. 31). In each casethe chip surface region 16 extends at a positive chip-surface angle tothe cutting edge 12. The chip-surface base 18 has a negative chip angle.Due to the raised shape of the chip surface 10 according to FIGS. 29 and81 there is an additional transition region 35 between the chip-surfaceregion 16 and the region 10. The embodiments shown in FIGS. 29 and 31are different from those according to FIGS. 28 through 30 only in thatthe first-named plates are indexable cutting plates, that is usable onboth sides.

As shown in FIGS. 32 and 33 the envelope curves of the chip surfaceregions 16 on the one hand and the path of their chip-surfaces bases 8on the other hand are convex (FIG. 32) or convex (FIG. 33). The shape ofthe envelope curve 36 generally follows the arcuate path of theconnecting lines of the individual indentations 14. The same is true forthe envelope curve 37 according to FIG. 33. According to the curvaturethere is in the cutting-corner region a negative or positive inclinationangle.

FIGS. 34 and 35 show respective embodiments of square indexable cuttingplates in the work position with the difference being that in the caseof the embodiment according to FIG. 34 the cutting edge 121 is set backin the region of the chip-surface base 18 relative to the cutting edge122 in the region of the chip surface 16 by a distance 38 that dependson the inclination angle of the surfaces 16 and 18 from each other. Inthe embodiment of FIG. 35 in contrast this spacing 38 is compensated forin that the chip-surface base 18, that is the cutting edge 121, isextended to the plane of the cutting edge 122.

FIGS. 36 through 44 show further possible variants. Thus for example thechip-surface region 39 seen in the cutting edge direction can dropbetween the indentations, that is can extend at an angle 40 or can rise(angle 41). In addition as shown in FIG. 38, even the chip-surface base18 of the indentations can be inclined at an angle 42 to the cuttingedge 12 even together with inclined chip surfaces 39 or correspondinglyrising chip surfaces as shown in FIG. 27.

In the embodiment according to FIG. 39 the chip-surface base 18 isconvexly curved. It is also possible as shown in FIG. 40 to form thechip-surface regions 16 between the indentations 14 nonlinearly, eitherconvex or concave (see FIG. 41).

Further variants corresponding to FIGS. 42 and 43 are constructed suchthat relative to imaginary planar trapezoid sides the actual trapezoidside path 43 is concave or convex as shown at reference 44. Finally itis possible as shown in FIG. 44 to form the chip-surface region 16between two indentations 14 arcuately, that is without straight parts.

In addition it is possible within the scope of the present invention toform the trapezoid side surfaces convexly at the border with the chipsurfaces 16 or chip-surface bases 18. As visible from FIG. 47 the actualtrapezoid side surfaces 47 each run concavely. A further variant whichcan be used in FIGS. 1, 13, 27 or 34, 38 and FIG. 45, 47 is that thelongitudinal axis. 46 runs at an acute angle 49 to a perpendicular 48 tothe cutting edge. Correspondingly the rear extent of the chip-surfacebase 18 is inclined.

I claim:
 1. In a cutting insert for chip-forming machining havinga chipsurface provided at a cutting edge with a plurality of indentationsarranged in a row extending along the cutting edge and each having agenerally trapezoidal sectional shape parallel to the cutting edge andperpendicular to the chip surface with trapezoidal sides open toward thechip surface, the improvement wherein the indentations each have achip-surface base extending at a substantially negative chip angle tothe cutting edge, the chip surface has in regions between theindentations at the cutting edge a positive chip angle of at least 5°,the indentations extend to and interrupt the cutting edge, andtransitions from each chip-surface base to the respective trapezoidalsides or from the trapezoidal sides to the respective chip-surfaceregions between the indentations are rounded to a radius of at least 0.3mm.
 2. The cutting insert according to claim 1 wherein the trapezoidalshape of the indentations is axially symmetrical to a perpendicular fromthe cutting edge.
 3. The cutting insert according to claim 1 wherein theindentations at cutting corners of the insert each have trapezoid sideswith a steep inclination angle or narrow trapezoidal bases or smallspacings between the indentations.
 4. The cutting insert according toclaim 1 wherein the trapezoidal sides open at angles of between 30° and80°.
 5. The cutting insert according to claim 4 wherein the negativechip angle of the trapezoidal base of the indentation lies between 0°and 20°.
 6. The cutting insert according to claim 4 wherein the negativechip angle of the trapezoidal base of the indentation lies between 5°and 15°.
 7. The cutting insert according to claim 1 wherein the positivechip angle of the chip surface surrounding the indentations is between5° and 25°.
 8. The cutting insert according to claim 1 wherein spacingsof the indentations at the cutting edge are smaller than the width ofthe indentations or increase uniformly with increasing spacing from thecutting edge.
 9. The cutting insert according to claim 8 wherein eachindentation seen in a top view on the chip surface is generallyrectangular.
 10. The cutting insert according to claim 8 wherein eachindentation seen in a top view on the chip surface is generallypreferably trapezoidal.
 11. The cutting insert according to claim 1wherein the width of each indentation at the cutting edge is between 0.5mm and 4 mm.
 12. The cutting insert according to claim 1 wherein thecutting edge has a bevel.
 13. The cutting insert according to claim 12wherein the angle between the bevel lying in the chip-surface plane andthe positive chip-surface region between the indentations itself as wellas between this bevel and the negative chip-surface base of theindentation is between 160° and 175°.
 14. The cutting insert accordingto claim 1 wherein the chip-surface base of the indentation or thesurrounding chip surface is formed with an additional chip groove. 15.The cutting insert according to claim 1 wherein the chip surfacesurrounding the insert has at a spacing from the cutting edge raisedchip-forming elements.
 16. The cutting insert according to claim 1wherein the chip surface has along the cutting edge from cutting cornerto cutting corner a convex or concave envelope curve.
 17. The cuttinginsert according to claim 16 wherein the depth or the spacing of theindentations increases from the cutting corners to a middle of thecutting edge.
 18. The cutting insert according to claim 1 wherein thetransitions are rounded with a radius of at most 3 mm.
 19. The cuttinginsert according to claim 1 wherein the positive chip angle of the chipsurface surrounding the indentations is between 5° and 20°.
 20. Thecutting insert according to claim 1 wherein the chip surface surroundingthe insert has at a spacing from the cutting edge raised chip-formingelements shaped as pyramidal or conical frustums.